1. Field of the Invention
The present invention relates to a compressor used for an air-conditioning system for vehicles, and specifically relates to a reciprocating type compressor used for an air-conditioning system for large-sized vehicles such as buses.
2. Description of the Related Art
As shown in FIG. 1, a compressor of this type comprises a front side cylinder block 2 in which front side cylinder bores 20 are formed, a rear side cylinder block 3 in which a rear side cylinder bores 30 are formed, a front head 5 assembled on the front side (on the left side in FIG. 1) of the front side cylinder block 2 with a valve plate 4 interposed therebetween, and a rear head 7 assembled on the rear side (on the right side in FIG. 1) of the rear side cylinder block 3 with a valve plate 6 interposed therebetween (see Utility Model Registration No. 3153200).
The front head 5, the valve plate 4, the front side cylinder block 2, the rear side cylinder block 3, the valve plate 6 and the rear head 7 are fastened in the axial direction by fastening bolts 8 to configure a housing of the compressor.
A plurality of the front side cylinder bores 20 formed on the front side cylinder block 2 and a plurality of the rear side cylinder bores 30 formed on the rear side cylinder block 3 are disposed at regular interval along respective virtual circumferences whose center is a shaft 16, and the cylinder bore 20 and the cylinder bore 30 which face each other are constructed in a manner that respective center lines are put together, so that the front side cylinder block 2 and the rear side cylinder block 3 define a crank chamber 10 therebetween. The cylinder blocks (the front side cylinder block 2 and the rear side cylinder block 3) further support the shaft which goes through the crank chamber 10.
Further, a swash plate 43 which is securely attached to the shaft 16 is provided in the crank chamber, and the shaft 16 is rotated and the swash plate 43 is rotated thereby so as to reciprocate each double-headed piston 40 sliding in the cylinder bore of the front side cylinder block 2 and the cylinder bore of the rear side cylinder block 3 which face each other. As a result, in each of the cylinder bores 20, 30, between the double-headed piston 40 inserted therein and the valve plates 4, 6, compression chamber 41, 42 whose capacity changes in accordance with movement of the double-headed piston 40 is defined.
On the respective valve plates 4, 6, suction holes 4a, 6a which are opened and closed by respective suction valves and discharge holes 4b, 6b which are opened and closed by respective discharge valves are formed, correspondingly to the respective cylinder bores 20, 30. On the front head 5 and the rear head 7, suction chambers 5a, 7a for containing refrigerant to be supplied to the compression chambers 41, 42 and discharge chambers 5b,7b for containing refrigerant discharged from the compression chambers 41, 42 are formed, respectively. The suction chambers 5a, 7a are formed approximately on the center of the front head 5 and the rear head 7, respectively, and the discharge chambers 5b, 7b are formed around the suction chambers 5a, 7a. 
Further in this example, the front side cylinder block 2 and the rear side cylinder block 3 have a pair of gas passages (a gas passage on the suction side 51, a gas passage on the discharge side 52) in the suction side and the outlet side that are formed along the axial direction of the shaft 16, which are deviated each other in the circumferential direction in a manner that run through both of the front side cylinder block 2 and the rear side cylinder block 3 as shown in FIGS. 7 and 8. The gas passage on the suction side 51 and the gas passage on the discharge side 52 are formed symmetrical to a plane containing an axis of the shaft 16 and located in the center of the both gas passages, and a gas port on the suction side 53 leading to the gas passage on the suction side 51 is provided on one of the front side cylinder block 2 and the rear side cylinder block 3 and a gas port on the discharge side 54 leading to the gas passage on the discharge side 52 is provided on the other thereof. The gas port on the suction side 53 is guided to the suction chambers 5a, 7a formed on the front head 5 and the rear head 7 through the gas passage on the suction side 51, and the gas port on the discharge side 54 is guided to the discharge chambers 5b, 7b formed on the front head 5 and the rear head 7 through the gas passage on the discharge side 52.
In refrigerant exchange work particularly for an air-conditioning system of large-sized vehicles such as buses, in which refrigerant of about 10 kg is enclosed in a reciprocating-type compressor like above, the exchange work requires disassembling a piping to discharge enclosed refrigerant and assemble the piping again to fill new refrigerant, thus requiring labor-intensive work and increased maintenance costs incurred for the work. To avoid such problems, pipes are connected to the gas port on the suction side 53 and the gas port on the discharge side 54 through a pipe connectors 60 which each has a shut off valve as shown in FIG. 7, and when the pipes are removed, the shut off valves are closed so as to prevent the outflow of the refrigerant between the compressor and refrigerating cycle system.
However, each pipe connector 60 is usually placed approximately perpendicular to an axial line of the compressor so that it protrudes toward the tangential direction from the peripheral wall of the compressor for the convenience of the pipe layout (because the pipe is connected at the side of the compressor). As shown in FIG. 8, if the gas port on the suction side 53 and the gas port on the discharge side 54 are formed right above the gas passage on the suction side 51 and the gas passage on the discharge side 52 respectively, one pipe connector 60 may be attached within space where a compressor is allowed to be mounted above the compressor, but the other pipe connector 60 excessively protrudes in the lateral direction of the compressor and interferes with adjacent objects (an engine or other auxiliary machines) which inconveniently makes impossible to place the compressor in the limited mounting space.
For this reason, in order to restrict the protrusion length of the pipe connector 60 in the lateral direction (protrusion amount in the tangential direction of the cylinder block), the gas port on the suction side and the gas port on the discharge side provided above the housing should be preferably arranged in parallel above an axis of the compressor (at approximately the midsection of the horizontal width perpendicular to an axis) along the axial line when viewed from above the housing as shown in FIG. 9.
However, since the gas passage on the suction side and the gas passage on the discharge side are extending along the axial direction in the cylinder block, and provided in parallel so as to be deviated each other in the circumferential direction, therefore if attempting to provide the gas port on the suction side and the gas port on the discharge direction in parallel along the axial line, it is impossible to realize such a configuration because each gas port cannot be placed right above the corresponding gas passage.
Further in the compressor of this type, front and back vibration due to compression reaction force is large and the reaction force is then transmitted to the cylinder block through the swash plate and the energy is radiated to the outside as a vibration of the compressor. For this reason, the compressor is designed so as to absorb the vibration by rigidity of the cylinder block and a thrust bearing which is interposed between the swash plate and the cylinder block and receives a thrust load of the swash plate. If, however, a shape of the cylinder block on the front side and that on the rear side are different, the rigidity is not equal, which easily results in a partial wear of a portion which receives the thrust load.
The present invention has been made with a view to such circumstances and mainly aims to provide a compressor enabling to make protrusion of the pipe connector in the lateral direction of the compressor smaller, which is to be provided to the cylinder block, and also aims at providing a reciprocating-type compressor, enabling to reduce the partial wear of a sliding contact portion which receives the thrust load of compressor inside structure.